1. Field of the Invention
The present invention relates to a wafer processing method for dividing a wafer along a plurality of crossing streets formed on the front side of the wafer, the wafer having a device area and a peripheral marginal area surrounding the device area, the device area being composed of a plurality of regions partitioned by the streets, wherein individual devices are respectively formed in the regions of the device area.
2. Description of the Related Art
In a semiconductor device fabrication process, a plurality of crossing division lines called streets are formed on the front side of a substantially disk-shaped semiconductor wafer to thereby partition a plurality of regions where devices such as ICs and LSIs are respectively formed. The semiconductor wafer is cut along these streets to thereby divide a device area into the individual devices. Prior to cutting the wafer along the streets, the back side of the wafer is ground or etched to reduce the thickness of the wafer to a predetermined finished thickness. In recent years, it has been required to reduce the wafer thickness to 50 μm or less in order to achieve a reduction in size and weight of electric equipment. However, such a reduction in wafer thickness to 50 μm or less causes easy damage to the wafer, so that handling such as transportation of the wafer is difficult.
To solve this problem, there has been disclosed a wafer processing method in Japanese Patent Laid-Open No. 2007-19461, for example. In this wafer processing method, the back side of a wafer is ground in an area corresponding to a device area to thereby reduce the thickness of the device area to a predetermined finished thickness and to simultaneously form an annular reinforcing portion in an area corresponding to a peripheral marginal area surrounding the device area, thereby increasing the rigidity of the wafer.
After grinding the back side of the wafer in the area corresponding to the device area to thereby reduce the thickness of the device area to a predetermined finished thickness and to simultaneously form the annular reinforcing portion in the area corresponding to the peripheral marginal area, the wafer is divided into the individual devices. In dividing the wafer into the individual devices, there is a problem such that when and how to remove the peripheral marginal area where the annular reinforcing portion is formed.